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5. Colistin + Meropenum + Vancomycin + Inhaled Colistin
Chronic bacterial infection in the viscous airway plugs is one of the major driving factors for the vicious cycle in cystic fibrosis. The most common pathogens include Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus, and Burkholderia cepacia complex, which are associated with a worse prognosis and higher mortality. Other pathogens frequently identified include Haemophilus influenza, Stenotrophomonas maltophilia, Achromobacter xylosoxidans, Mycobacterium avium complex and Aspergillus species. The initial bacterial infection can be cured by intravenous antibiotic treatment, however as the disease progresses, chronic infection develops from biofilm formation causing poor antibiotic penetration and acquired or native resistance. Therefore, current guideline recommends periodic cultures to guide antibiotic treatment when the patient experiences an acute pulmonary exacerbation (20).
For pseudomonal infection, combination treatment of tobramycin with other anti-pseudomonal agents including a third generation cephalosporin, carbapenem or aztreoman is the most commonly used regimen, and the benefit of using two different classes of anti-pseudomonal antibiotics rather than single regimen has been shown (21). However, in cases with multi-drug resistant pseudomonal infection as in our case, IV colistin in combination with other anti-pseudomonal agents (except an aminoglycoside due to renal toxicity) is recommended since the goal of antibiotic treatment in this setting is reducing the bacterial burden rather than eradication. Moreover, by using concomitant inhaled colistin, the systemic toxicity from intravenous colistin can be reduced. For MRSA, vancomycin or linezolide are recommended antibiotics.
The optimal duration of antibiotic treatment in pulmonary exacerbation remains unknown. Current guideline recommends IV antibiotic treatment until symptoms and signs of pulmonary exacerbation resolve with a minimum of 10 days treatment.
Our patient was initially put on mechanical ventilation with settings of volume control, TV 400 ml, FiO2 100 %, RR 36, PEEP 10 cm H2O. However, hypoxemia and hypercapnia were refractory even with multiple trials of ventilator adjustment. Moreover, patient developed hypotension with BP of 60/30 mmHg and acute kidney injury with her creatinine rising to 2.4 mg/dL (baseline 0.8), requiring levophed, vasopressin, epinephrine, steroids and continuous renal replacement therapy. ABG on above ventilator setting were as follows: pH 7.06, pCO2 78.1mmHg, pO2 126 mmHg, HCO3- 22.1meq/L and SaO2 91.8%.
Chest x-ray and chest CT are shown in Figure 5.
Figure 5. Chest x-ray AP (Panel A) and representative image from chest CT scan (Panel B).
What are possible alternative treatment(s) for this patient? (Click on the correct answer to move to the next panel)